Multi-speed transmission

ABSTRACT

A transmission is provided having an input member, an output member, four planetary gear sets, a plurality of coupling members and a plurality of torque transmitting devices. Each of the planetary gear sets includes first, second and third members. The torque transmitting devices may include clutches and brakes. The torque transmitting devices are selectively engageable in combinations of at least two to establish at least eight forward speed ratios and at least one reverse speed ratio between the input member and the output member.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.60/913,146 filed on Apr. 20, 2007. The disclosure of the aboveapplication is incorporated herein by reference.

FIELD

The invention relates generally to a multiple speed transmission havinga plurality of planetary gear sets and a plurality of torquetransmitting devices and more particularly to a transmission havingeight or more speeds, four planetary gear sets and a plurality of torquetransmitting devices.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may or may not constitute priorart.

A typical multiple speed transmission uses a combination of frictionclutches, planetary gear arrangements and fixed interconnections toachieve a plurality of gear ratios. The number and physical arrangementof the planetary gear sets, generally, are dictated by packaging, costand desired speed ratios.

While current transmissions achieve their intended purpose, the need fornew and improved transmission configurations which exhibit improvedperformance, especially from the standpoints of efficiency,responsiveness and smoothness and improved packaging, primarily reducedsize and weight, is essentially constant. Accordingly, there is a needfor an improved, cost-effective, compact multiple speed transmission.

SUMMARY

In an embodiment of the present invention, a transmission is providedhaving an input member, an output member, four planetary gear sets, aplurality of coupling members and a plurality of torque transmittingdevices. Each of the planetary gear sets includes first, second andthird members. A first interconnecting member continuously interconnectsthe first member of the first planetary gear set with second member ofthe second planetary gear set. A second interconnecting membercontinuously interconnects the second member of the first planetary gearset with third member of the second planetary gear set. A thirdinterconnecting member continuously interconnects the first member ofthe second planetary gear set with the second member of the thirdplanetary gear set. A fourth interconnecting member continuouslyinterconnects the first member of the third planetary gear set with thefirst member of the fourth planetary gear set. Five torque transmittingdevices are selectively engageable to interconnect one of the firstmembers, second members, and third members with at least one other ofthe first members, second members, third members, and a stationarymember. The torque transmitting devices are selectively engageable incombinations of at least two to establish at least eight forward speedratios and at least one reverse speed ratio between the input member andthe output member.

In another embodiment of the present invention a transmission isprovided having an input member, an output member, four planetary gearsets, a plurality of coupling members and a plurality of torquetransmitting devices. The first, second, third and fourth planetary gearsets each having a sun gear, a carrier member and a ring gear. The inputmember is continuously interconnected with the sun gear of the firstplanetary gear set and the output member is continuously interconnectedwith the carrier member of the fourth planetary gear set. A firstinterconnecting member continuously interconnects the ring gear of thefirst planetary gear set with carrier member of the second planetarygear set. A second interconnecting member continuously interconnects thecarrier member of the first planetary gear set with sun gear of thesecond planetary gear set and ring gear of the fourth planetary gearset. A third interconnecting member continuously interconnects the ringgear of the second planetary gear set with the carrier member of thethird planetary gear set. A fourth interconnecting member continuouslyinterconnects the ring gear of the third planetary gear set with thering gear of the fourth planetary gear set. A first torque transmittingdevice is selectively engageable to interconnect the carrier member ofthe third planetary gear set with the carrier member of the fourthplanetary gear set. A second torque transmitting device is selectivelyengageable to interconnect the carrier member of the third planetarygear set with the sun gear of the fourth planetary gear set. A thirdtorque transmitting device is selectively engageable to interconnect thesun gear of the third planetary gear set with the stationary member. Afourth torque transmitting device is selectively engageable tointerconnect the sun gear of the fourth planetary gear set with thestationary member. A fifth torque transmitting device is selectivelyengageable to interconnect the carrier member of the second planetarygear set with the stationary member. The torque transmitting devices areselectively engageable in combinations of at least two to establish atleast eight forward speed ratios and at least one reverse speed ratiobetween the input member and the output member.

In yet another embodiment of the present invention a transmission isprovided having an input member, an output member, four planetary gearsets, a plurality of coupling members and a plurality of torquetransmitting devices. The first, second, third and fourth planetary gearsets each having a sun gear, a carrier member and a ring gear. The inputmember is continuously interconnected with at least one of the carriermember of the first planetary gear set and the sun gear of the secondplanetary gear set. The output member is continuously interconnectedwith the carrier member of the fourth planetary gear set. A firstinterconnecting member continuously interconnects the ring gear of thefirst planetary gear set with carrier member of the second planetarygear set. A second interconnecting member continuously interconnects thecarrier member of the first planetary gear set with sun gear of thesecond planetary gear set. A third interconnecting member continuouslyinterconnects the ring gear of the second planetary gear set with thecarrier member of the third planetary gear set. A fourth interconnectingmember continuously interconnects the ring gear of the first planetarygear set with the ring gear of the third planetary gear set and the ringgear of the fourth planetary gear set. The first torque transmittingdevice is selectively engageable to interconnect the carrier member ofthe fourth planetary gear set with the sun gear of the third planetarygear set. The second torque transmitting device is selectivelyengageable to interconnect the sun gear of the fourth planetary gear setwith the sun gear of the third planetary gear set. The third torquetransmitting device is selectively engageable to interconnect the ringgear of the second planetary gear set with the stationary member. Thefourth torque transmitting device is selectively engageable tointerconnect the sun gear of the first planetary gear set with thestationary member. The fifth torque transmitting device is selectivelyengageable to interconnect the sun gear of the fourth planetary gear setwith the stationary member. The torque transmitting devices areselectively engageable in combinations of at least two to establish atleast eight forward speed ratios and at least one reverse speed ratiobetween the input member and the output member.

Further aspects and advantages of the present invention will becomeapparent by reference to the following description and appended drawingswherein like reference numbers refer to the same component, element orfeature.

DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1 is a lever diagram of an embodiment of an eight speedtransmission according to the present invention;

FIG. 2 is a diagrammatic view of an embodiment of an eight speedtransmission according to the present invention; and

FIG. 3 is a truth table presenting the state of engagement of thevarious torque transmitting clutches and brakes in each of the availableforward and reverse speeds or gear ratios of the transmissionillustrated in FIGS. 1 and 2.

FIG. 4 is a lever diagram of another embodiment of an eight speedtransmission according to the present invention;

FIG. 5 is a diagrammatic view of another embodiment of an eight speedtransmission according to the present invention; and

FIG. 6 is a truth table presenting the state of engagement of thevarious torque transmitting clutches and brakes in each of the availableforward and reverse speeds or gear ratios of the transmissionillustrated in FIGS. 4 and 5.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses.

At the outset, it should be appreciated that the embodiments of theeight speed automatic transmission of the present invention have anarrangement of permanent mechanical connections between the elements ofthe four planetary gear sets in common. These mechanical connectionsgenerically link or relate the transmission embodiments. A firstcomponent or element of a first planetary gear set is permanentlycoupled to a second component or element of a second planetary gear set.A second component or element of the first planetary gear set ispermanently coupled to a third component or element of a secondplanetary gear set. A first component or element of the second planetarygear set is permanently coupled to a second component or element of athird planetary gear set. A first component or element of the thirdplanetary gear set is permanently coupled to a first component orelement of a fourth planetary gear set.

Referring now to FIG. 1, an embodiment of an eight speed transmission 10is illustrated in a lever diagram format. A lever diagram is a schematicrepresentation of the components of a mechanical device such as anautomatic transmission. Each individual lever represents a planetarygear set wherein the three basic mechanical components of the planetarygear are each represented by a node. Therefore, a single lever containsthree nodes: one for the sun gear, one for the planet gear carrier, andone for the ring gear. The relative length between the nodes of eachlever can be used to represent the ring-to-sun ratio of each respectivegear set. These lever ratios, in turn, are used to vary the gear ratiosof the transmission in order to achieve an appropriate ratios and ratioprogression. Mechanical couplings or interconnections between the nodesof the various planetary gear sets are illustrated by thin, horizontallines and torque transmitting devices such as clutches and brakes arepresented as interleaved fingers. If the device is a brake, one set ofthe fingers is grounded. Further explanation of the format, purpose anduse of lever diagrams can be found in SAE Paper 810102, “The LeverAnalogy: A New Tool in Transmission Analysis” by Benford and Leisingwhich is hereby fully incorporated by reference.

The transmission 10 includes an input shaft or member 12, a firstplanetary gear set 14 having three nodes: a first node 14A, a secondnode 14B and a third node 14C, a second planetary gear set 16 havingthree nodes: a first node 16A, a second node 16B and a third node 16C, athird planetary gear set 18 having three nodes: a first node 18A, asecond node 18B and a third node 18C, a fourth planetary gear set 20having three nodes: a first node 20A, a second node 20B and a third node20C and an output shaft or member 22.

The input 12 is coupled to the third node 14C of the first planetarygear set. The output 22 is coupled to the second node 20B of the fourthplanetary gear set 20. The first node 14A of the first planetary gearset 14 is coupled to the second node 16B of the second planetary gearset 16. The second node 14B of the first planetary gear set 14 iscoupled to the third node 16C of the second planetary gear set 16 and toa first node 20A of the fourth planetary gear set 20. The first node 16Aof the second planetary gear set 16 is coupled to the second node 18B ofthe third planetary gear set 18. The first node 18A of the thirdplanetary gear set 18 is coupled to a first node 20A of the fourthplanetary gear set 20.

A first clutch 26 selectively connects the second node 18B of the thirdplanetary gear set 18 to the second node 20B of the fourth planetarygear set 20. A second clutch 28 selectively connects the second node 18Bof the third planetary gear set 18 to the third node 20C of the fourthplanetary gear set 20. A first brake 30 selectively connects the thirdnode 18C of the third planetary gear set 18 to the ground ortransmission housing 50. A second brake 32 selectively connects thethird node 20C of the fourth planetary gear set 20 to the ground ortransmission housing 50. A third brake 34 selectively connects thesecond node 16B of the second planetary gear set 16 to the ground ortransmission housing 50.

Referring now to FIG. 2, a stick diagram presents a schematic layout ofthe embodiment of the eight speed transmission 10 according to thepresent invention. In FIG. 2, the numbering from the lever diagram ofFIG. 1 is carried over. The clutches, brakes and couplings arecorrespondingly presented whereas the nodes of the planetary gear setsnow appear as components of planetary gear sets such as sun gears, ringgears, planet gears and planet gear carriers.

For example, planetary gear set 14 is a planetary gear set that includesa sun gear member 14C, a planet gear carrier member 14B and a ring gearmember 14A. Sun gear member 14C is connected for common rotation withinput shaft or member 12. Ring gear member 14A is connected to a firstinterconnecting shaft or member 52. The planet gear carrier member 14Brotatably supports a set of planet gears 14D (only one shown) and isconnected for common rotation with a second interconnecting shaft ormember 54 and a third interconnecting shaft or member 56. Planet gears14D are configured to intermesh with sun gear member 14C and ring gearmember 14A.

The input shaft or member 12 is continuously connected to an engine (notshown) or to a turbine of a torque converter (not shown). The outputshaft or member 22 is continuously connected with the final drive unitor transfer case (not shown).

Planetary gear set 16 is a planetary gear set that includes a sun gearmember 16C, a planet carrier member 16B that rotatably supports a set ofplanet gears 16D and a ring gear member 16A. Sun gear member 16C isconnected for common rotation with the second interconnecting shaft ormember 54. Planet carrier member 16B is connected for common rotationwith first interconnecting shaft or member 52 and a first outer shaft ormember 58. Ring gear member 16A is connected for common rotation with afourth interconnecting shaft or member 60. Planet gears 16D areconfigured to intermesh with both sun gear member 16C and ring gearmember 16A.

Planetary gear set 18 is a planetary gear set that includes a sun gearmember 18C, a ring gear member 18A and a planet carrier member 18B thatrotatably supports a set of planet gears 18D. Sun gear member 18C isconnected for common rotation with a second outer shaft or member 62.Ring gear member 18A is connected for common rotation with the thirdinterconnecting shaft or member 56. Planet carrier member 18B isconnected for common rotation with fourth interconnecting shaft ormember 60 and a fifth interconnecting shaft or member 64. Planet gears18D are configured to intermesh with both sun gear member 18C and ringgear member 18A.

Planetary gear set 20 is a planetary gear set that includes a sun gearmember 20C, a ring gear member 20A and a planet carrier member 20B thatrotatably supports a set of planet gears 20D. Sun gear member 20C isconnected for common rotation with a sixth interconnecting shaft ormember 66. Ring gear member 20B is connected for common rotation withthird interconnecting shaft or member 56. Planet carrier member 20B isconnected for common rotation with a seventh interconnecting shaft ormember 68 and output shaft or member 22. Planet gears 20D are configuredto intermesh with both sun gear member 20C and ring gear member 20A.

The torque-transmitting mechanisms or clutches 26, 28 and brakes 30, 32and 34 allow for selective interconnection of the shafts orinterconnecting members, members of the planetary gear sets and thehousing. For example, the first clutch 26 is selectively engageable toconnect the fifth interconnecting shaft or member 64 to the seventhinterconnecting shaft or member 68. The second clutch 28 is selectivelyengageable to connect the fifth interconnecting member 64 to the sixthinterconnecting shaft or member 66. The first brake 30 is selectivelyengageable to connect second outer shaft or member 62 to the ground ortransmission housing 50 to restrict rotation of the member 62 relativeto the housing 50. The second brake 32 is selectively engageable toconnect sixth interconnecting shaft or member 66 to the ground ortransmission housing 50 to restrict rotation of the member 66 relativeto the housing 50. The third brake 34 is selectively engageable toconnect the first outer shaft or member 58 to the ground or transmissionhousing 50 to restrict rotation of the member 58 relative to the housing50.

Referring now to FIGS. 2 and 3, the operation of the embodiment of theeight speed transmission 10 will be described. It will be appreciatedthat transmission 10 is capable of transmitting torque from the inputshaft or member 12 to the output shaft or member 22 in at least eightforward speed or torque ratios and at least one reverse speed or torqueratio. Each forward and reverse speed or torque ratio is attained byengagement of one or more of the torque-transmitting mechanisms (i.e.first clutch 26, second clutch 28, first brake 30, second brake 32, andthird brake 34), as will be explained below. FIG. 3 is a truth tablepresenting the various combinations of torque-transmitting mechanismsthat are activated or engaged to achieve the various gear states. Actualnumerical gear ratios of the various gear states are also presentedalthough it should be appreciated that these numerical values areexemplary only and that they may be adjusted over significant ranges toaccommodate various applications and operational criteria of thetransmission 10. An example of the gear ratios that may be obtainedusing the embodiments of the present invention are also shown in FIG. 3.Of course, other gear ratios are achievable depending on the geardiameter, gear teeth count and gear configuration selected.

To establish reverse gear, the first clutch 26 and the third brake 34are engaged or activated. The first clutch 26 connects the fifthinterconnecting shaft or member 64 to the seventh interconnecting shaftor member 68. The third brake 34 connects the first outer shaft ormember 58 to the ground or transmission housing 50 to restrict rotationof the member 58 relative to the housing 50.

Likewise, the eight forward ratios are achieved through differentcombinations of clutch engagement, as shown in FIG. 3.

It will be appreciated that the foregoing explanation of operation andgear states of the eight speed transmission 10 assumes, first of all,that all the clutches and the brake not specifically referenced in agiven gear state are inactive or disengaged and, second of all, thatduring gear shifts, i.e., changes of gear state, between at leastadjacent gear states, a clutch or brake engaged or activated in bothgear states will remain engaged or activated.

Referring now to FIG. 4, another embodiment of a transmission isillustrated and referenced by reference numeral 100. Transmission 100includes an input shaft or member 112, a first planetary gear set 114having three nodes: a first node 114A, a second node 114B and a thirdnode 114C, a second planetary gear set 116 having three nodes: a firstnode 116A, a second node 116B and a third node 116C, a third planetarygear set 118 having three nodes: a first node 118A, a second node 118Band a third node 118C, a fourth planetary gear set 120 having threenodes: a first node 120A, a second node 120B and a third node 120C andan output shaft or member 122.

The input 112 is coupled to the third node 116C of the first planetarygear set 116. The output 122 is coupled to the second node 120B of thefourth planetary gear set 120. The first node 114A of the firstplanetary gear set 114 is coupled to the second node 116B of the secondplanetary gear set 116 and to the first node 118A of the third planetarygear set 118. The second node 114B of the first planetary gear set 114is coupled to the third node 116C of the second planetary gear set 116.The first node 116A of the second planetary gear set 116 is coupled tothe second node 118B of the third planetary gear set 118. The first node118A of the third planetary gear set 118 is coupled to a first node 120Aof the fourth planetary gear set 120.

A first clutch 126 selectively connects the third node 118C of the thirdplanetary gear set 118 to the second node 120B of the fourth planetarygear set 120. A second clutch 128 selectively connects the third node118C of the third planetary gear set 118 to the third node 120C of thefourth planetary gear set 120. A first brake 130 selectively connectsthe first node 116A of the second planetary gear set 116 to the groundor transmission housing 150. A second brake 132 selectively connects thethird node 114C of the first planetary gear set 114 to the ground ortransmission housing 150. A third brake 134 selectively connects thethird node 120C of the fourth planetary gear set 120 to the ground ortransmission housing 150.

Referring now to FIG. 5, a stick diagram presents a schematic layout ofthe embodiment of the eight speed transmission 100 according to thepresent invention. In FIG. 5, the numbering from the lever diagram ofFIG. 4 is carried over. The clutches, brakes and couplings arecorrespondingly presented whereas the nodes of the planetary gear setsnow appear as components of planetary gear sets such as sun gears, ringgears, planet gears and planet gear carriers.

For example, planetary gear set 114 is a planetary gear set thatincludes a sun gear member 114C, a planet gear carrier member 114B and aring gear member 114A. Sun gear member 114C is connected for commonrotation with a first interconnecting shaft or member 142. Ring gearmember 114A is connected to a second interconnecting shaft or member 144and a third interconnecting shaft or member 146. The planet gear carriermember 114B rotatably supports a set of planet gears 114D (only oneshown) and is connected for common rotation with a fourthinterconnecting shaft or member 148 and the input shaft or member 112.Planet gears 114D are configured to intermesh with sun gear member 114Cand ring gear member 114A.

The input shaft or member 112 is continuously connected to an engine(not shown) or to a turbine of a torque converter (not shown). Theoutput shaft or member 122 is continuously connected with the finaldrive unit or transfer case (not shown).

Planetary gear set 116 is a planetary gear set that includes a sun gearmember 116C, a planet carrier member 116B that rotatably supports a setof planet gears 116D and a ring gear member 116A. Sun gear member 116Cis connected for common rotation with the fourth interconnecting shaftor member 148. Planet carrier member 116B is connected for commonrotation with second interconnecting shaft or member 144. Ring gearmember 116A is connected for common rotation with a fifthinterconnecting shaft or member 152 and a sixth interconnecting shaft ormember 154. Planet gears 116D are configured to intermesh with both sungear member 116C and ring gear member 116A.

Planetary gear set 118 is a planetary gear set that includes a sun gearmember 118C, a ring gear member 118A and a planet carrier member 118Bthat rotatably supports a set of planet gears 118D. Sun gear member 118Cis connected for common rotation with a seventh interconnecting shaft ormember 156. Ring gear member 118A is connected for common rotation withthird interconnecting shaft or member 146. Planet carrier member 118B isconnected for common rotation with sixth interconnecting shaft or member154. Planet gears 118D are configured to intermesh with both sun gearmember 118C and ring gear member 118A.

Planetary gear set 120 is a planetary gear set that includes a sun gearmember 120C, a ring gear member 120A and a planet carrier member 120Bthat rotatably supports a first set of planet gears 120D and a secondset of planet gears 120E. Sun gear member 120C is connected for commonrotation with an eighth interconnecting shaft or member 158. Ring gearmember 120A is connected for common rotation with the thirdinterconnecting shaft or member 146. Planet carrier member 120B isconnected for common rotation with a ninth interconnecting shaft ormember 160 and output shaft or member 122. The first planet gears 120Dare configured to intermesh with the sun gear member 120C and the secondplanet gears 120E are configured to intermesh with the ring gear member120A. The first and second planet gears 120D and 120E are configured tointermesh with one another.

The torque-transmitting mechanisms or clutches 126, 128 and brakes 130,132 and 134 allow for selective interconnection of the shafts orinterconnecting members, members of the planetary gear sets and thehousing 150. For example, the first clutch 126 is selectively engageableto connect the seventh interconnecting shaft or member 156 to the ninthinterconnecting shaft or member 160. The second clutch 128 isselectively engageable to connect the seventh interconnecting shaft ormember 156 to eighth interconnecting shaft or member 158. The firstbrake 130 is selectively engageable to connect the fifth interconnectingshaft or member 152 to the ground or housing 150 to restrict rotation ofthe member 152 relative to the ground or housing 150. The second brake132 is selectively engageable to connect the first interconnecting shaftor member 142 to the ground or housing 150 to restrict rotation of themember 142 relative to the ground or housing 150. The third brake 134 isselectively engageable to connect the eighth interconnecting member 158to the ground or housing 150 to restrict rotation of the eighthinterconnecting member 158 relative to the ground or housing 150.

Referring now to FIGS. 5 and 6, the operation of the embodiment of theeight speed transmission 100 will be described. It will be appreciatedthat the transmission 100 is capable of transmitting torque from theinput shaft or member 112 to the output shaft or member 122 in at leasteight forward speeds or torque ratios and at least one reverse speed ortorque ratio. Each forward and reverse speed or torque ratio is attainedby engagement of one or more of the torque-transmitting mechanisms (i.e.first clutch 126, second clutch 128, first brake 130, second brake 132and third brake 134), as will be explained below. FIG. 6 is a truthtable presenting the various combinations of torque-transmittingmechanisms that are activated or engaged to achieve the various gearstates. Actual numerical gear ratios of the various gear states are alsopresented although it should be appreciated that these numerical valuesare exemplary only and that they may be adjusted over significant rangesto accommodate various applications and operational criteria of thetransmission 100. An example of the gear ratios that may be obtainedusing the embodiments of the present invention are also shown in FIG. 6.Of course, other gear ratios are achievable depending on the geardiameter, gear teeth count and gear configuration selected.

To establish reverse gear, the first clutch 126 and the first brake 130are engaged or activated. The first clutch 126 connects the seventhinterconnecting shaft or member 156 to the ninth interconnecting shaftor member 160. The first brake 130 connects the fifth interconnectingshaft or member 152 to the ground or housing 150 to restrict rotation ofthe member 152 relative to the ground or housing 150.

Likewise, the eight forward ratios are achieved through differentcombinations of clutch and brake engagement, as shown in FIG. 6.

It will be appreciated that the foregoing explanation of operation andgear states of the eight speed transmission 100 assumes, first of all,that all clutches and brakes not specifically referenced in a given gearstate are inactive or disengaged and, second of all, that during gearshifts, i.e., changes of gear state, between at least adjacent gearstates, a clutch or brake engaged or activated in both gear states willremain engaged or activated.

The description of the invention is merely exemplary in nature andvariations that do not depart from the gist of the invention areintended to be within the scope of the invention. Such variations arenot to be regarded as a departure from the spirit and scope of theinvention.

1. A transmission comprising: an input member; an output member; first,second, third and fourth planetary gear sets each having first, secondand third members, wherein the input member is continuouslyinterconnected with the third member of the first planetary gear set; afirst interconnecting member continuously interconnecting the firstmember of the first planetary gear set with second member of the secondplanetary gear set; a second interconnecting member continuouslyinterconnecting the second member of the first planetary gear set withthird member of the second planetary gear set; a third interconnectingmember continuously interconnecting the first member of the secondplanetary gear set with the second member of the third planetary gearset; a fourth interconnecting member continuously interconnecting thefirst member of the third planetary gear set with the first member ofthe fourth planetary gear set; and five torque transmitting devices eachselectively engageable to interconnect at least one of the firstmembers, second members, and third members of the planetary gear setswith at least one other of the first members, second members, thirdmembers of the planetary gear sets, and a stationary member; and whereina first of the five torque transmitting devices is selectivelyengageable to interconnect the second member of the third planetary gearset with the second member of the fourth planetary gear set and thetorque transmitting devices are selectively engageable in combinationsof at least two to establish at least eight forward speed ratios and atleast one reverse speed ratio between the input member and the outputmember.
 2. The transmission of claim 1 wherein a second of the fivetorque transmitting devices is selectively engageable to interconnectthe second member of the third planetary gear set with the third memberof the fourth planetary gear set.
 3. The transmission of claim 2 whereina third of the five torque transmitting devices is selectivelyengageable to interconnect the third member of the third planetary gearset with the stationary member.
 4. The transmission of claim 3 wherein afourth of the five torque transmitting devices is selectively engageableto interconnect the third member of the fourth planetary gear set withthe stationary member.
 5. The transmission of claim 4 wherein a fifth ofthe five torque transmitting devices is selectively engageable tointerconnect the second member of the second planetary gear set with thestationary member.
 6. The transmission of claim 1 wherein the thirdmembers of the first, second, third and fourth planetary gear sets aresun gears, the second members of the first, second, third and fourthplanetary gear sets are carrier members and the first members of thefirst, second, third and fourth planetary gear sets are ring gears. 7.The transmission of claim 1 wherein the output member is continuouslyinterconnected with the second member of the fourth planetary gear set.8. The transmission of claim 1 wherein the stationary member is atransmission housing.
 9. A transmission comprising: an input member; anoutput member; first, second, third and fourth planetary gear sets eachhaving first, second and third members, wherein the input member iscontinuously interconnected with the third member of the first planetarygear set and the output member is continuously interconnected with thesecond member of the fourth planetary gear set; a first interconnectingmember continuously interconnecting the first member of the firstplanetary gear set with second member of the second planetary gear set;a second interconnecting member continuously interconnecting the secondmember of the first planetary gear set with third member of the secondplanetary gear set and first member of the fourth planetary gear set; athird interconnecting member continuously interconnecting the firstmember of the second planetary gear set with the second member of thethird planetary gear set; a fourth interconnecting member continuouslyinterconnecting the first member of the third planetary gear set withthe first member of the fourth planetary gear set; a first torquetransmitting device selectively engageable to interconnect the secondmember of the third planetary gear set with the second member of thefourth planetary gear set; a second torque transmitting deviceselectively engageable to interconnect the second member of the thirdplanetary gear set with the third member of the fourth planetary gearset; a third torque transmitting device selectively engageable tointerconnect the third member of the third planetary gear set with thestationary member; a fourth torque transmitting device selectivelyengageable to interconnect the third member of the fourth planetary gearset with the stationary member; and a fifth torque transmitting deviceselectively engageable to interconnect the second member of the secondplanetary gear set with the stationary member, and wherein the torquetransmitting devices are selectively engageable in combinations of atleast two to establish at least eight forward speed ratios and at leastone reverse speed ratio between the input member and the output member.10. The transmission of claim 9 wherein the third members of the first,second, third and fourth planetary gear sets are sun gears, the secondmembers of the first, second, third and fourth planetary gear sets arecarrier members and the first members of the first, second, third andfourth planetary gear sets are ring gears.
 11. The transmission of claim9 wherein the stationary member is a transmission housing.
 12. Atransmission comprising: an input member; an output member; first,second, third and fourth planetary gear sets each having a sun gear, acarrier member, and a ring gear, wherein the input member iscontinuously interconnected with the sun gear of the first planetarygear set and the output member is continuously interconnected with thecarrier member of the fourth planetary gear set; a first interconnectingmember continuously interconnecting the ring gear of the first planetarygear set with carrier member of the second planetary gear set; a secondinterconnecting member continuously interconnecting the carrier memberof the first planetary gear set with sun gear of the second planetarygear set and ring gear of the fourth planetary gear set; a thirdinterconnecting member continuously interconnecting the ring gear of thesecond planetary gear set with the carrier member of the third planetarygear set; a fourth interconnecting member continuously interconnectingthe ring gear of the third planetary gear set with the ring gear of thefourth planetary gear set; and a first torque transmitting deviceselectively engageable to interconnect the carrier member of the thirdplanetary gear set with the carrier member of the fourth planetary gearset; a second torque transmitting device selectively engageable tointerconnect the carrier member of the third planetary gear set with thesun gear of the fourth planetary gear set; a third torque transmittingdevice selectively engageable to interconnect the sun gear of the thirdplanetary gear set with the stationary member; a fourth torquetransmitting device selectively engageable to interconnect the sun gearof the fourth planetary gear set with the stationary member; and a fifthtorque transmitting device selectively engageable to interconnect thecarrier member of the second planetary gear set with the stationarymember, and wherein the torque transmitting devices are selectivelyengageable in combinations of at least two to establish at least eightforward speed ratios and at least one reverse speed ratio between theinput member and the output member.